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68ab47e4b4
Returning a partial object on error is an invitation for a careless
caller to leak memory. We already fixed things in an earlier
patch to guarantee NULL if visit_start fails ("qapi: Guarantee
NULL obj on input visitor callback error"), but that does not
help the case where visit_start succeeds but some other failure
happens before visit_end, such that we leak a partially constructed
object outside visit_type_FOO(). As no one outside the testsuite
was actually relying on these semantics, it is cleaner to just
document and guarantee that ALL pointer-based visit_type_FOO()
functions always leave a safe value in *obj during an input visitor
(either the new object on success, or NULL if an error is
encountered), so callers can now unconditionally use
qapi_free_FOO() to clean up regardless of whether an error occurred.
The decision is done by adding visit_is_input(), then updating the
generated code to check if additional cleanup is needed based on
the type of visitor in use.
Note that we still leave *obj unchanged after a scalar-based
visit_type_FOO(); I did not feel like auditing all uses of
visit_type_Enum() to see if the callers would tolerate a specific
sentinel value (not to mention having to decide whether it would
be better to use 0 or ENUM__MAX as that sentinel).
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1461879932-9020-25-git-send-email-eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
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| .. | ||
| specs | ||
| aio_notify.promela | ||
| aio_notify_accept.promela | ||
| aio_notify_bug.promela | ||
| atomics.txt | ||
| bitmaps.md | ||
| blkdebug.txt | ||
| blkverify.txt | ||
| bootindex.txt | ||
| build-system.txt | ||
| ccid.txt | ||
| ich9-ehci-uhci.cfg | ||
| image-fuzzer.txt | ||
| live-block-ops.txt | ||
| memory-hotplug.txt | ||
| memory.txt | ||
| migration.txt | ||
| multi-thread-compression.txt | ||
| multiple-iothreads.txt | ||
| multiseat.txt | ||
| pci_expander_bridge.txt | ||
| q35-chipset.cfg | ||
| qapi-code-gen.txt | ||
| qcow2-cache.txt | ||
| qdev-device-use.txt | ||
| qemupciserial.inf | ||
| qmp-events.txt | ||
| qmp-intro.txt | ||
| qmp-spec.txt | ||
| rcu.txt | ||
| rdma.txt | ||
| replay.txt | ||
| spice-port-fqdn.txt | ||
| throttle.txt | ||
| tracing.txt | ||
| usb-storage.txt | ||
| usb2.txt | ||
| virtio-balloon-stats.txt | ||
| virtio-migration.txt | ||
| vnc-ledstate-Pseudo-encoding.txt | ||
| win32-qemu-event.promela | ||
| writing-qmp-commands.txt | ||
| xbzrle.txt | ||
| xen-save-devices-state.txt | ||